Electrostatic suspension furnace and method for fusing samples using this

ABSTRACT

An electrostatic levitation furnace wherein main electrodes opposed to each other within a vacuum chamber are arranged at intervals to form interspaces between them. Auxiliary electrodes are arranged to correspond to each of the electrostatic field generating interspaces, and laser irradiators are arranged above the uppermost main electrode and under the lowermost main electrode, and the main electrode positioned midway between the uppermost and lowest one has a through-hole on an optical path of laser beam which a sample can be passed through. When two species of samples are fused together, regardless of whether or not the samples are conductors, the furnace has the function of melting the levitated samples and fusing them together while maintaining each of the temperatures of the samples, and consequently this permits realization of fusion in a state free of external interference.

This is a National Stage entry of International ApplicationPCT/JP2004/002190, with an international filing date of Feb. 25, 2004,which was published as WO 2004/083757 A1, and the complete disclosure ofwhich is incorporated into this application by reference.

TECHNICAL FIELD

The present invention relates to an electrostatic levitation furnace forputting a charged sample in a levitation state by electrostatic fieldgenerated between electrodes and performing heating process on thesample.

BACKGROUND ART

In a conventional art, an electrostatic levitation furnace where a pairof main electrodes is allocated in a flat and approximately cylindricalvacuum chamber on Z axis corresponding to an axis of the chamber, andalso a pair of auxiliary electrodes is allocated on each of X axis and Yaxis orthogonal to Z axis is well known.

The electrostatic levitation furnace charges a sample which is inputtedbetween main electrodes by electrode contact, ultraviolet irradiation,or heating in advance, puts the sample in a levitation state byelectrostatic field generated between main electrodes, and whilemaintaining the sample in a predetermined position by controlling aelectric potential between main electrodes or between auxiliaryelectrodes, irradiates a laser beam on the sample to heat and melt thesame. To cool and solidify the sample which is heated and melted in thisway enables to generate crystals in a state excluded from externalinterference (i.e. in a state avoided the use of a container).

The conventional electrostatic levitation furnace mentioned above hasthe function of melting a sample maintained in a levitation state, butdoes not have the one of melting two or more species of samples whilelevitating because of incapable of putting a plurality of samples in alevitation state using one electrostatic field.

As an electrostatic levitation furnace except for the one mentionedabove, an electromagnetic levitation furnace which levitates a sampleelectromagnetically is well known. For example, when two species ofsamples are fused together using the aforesaid electromagneticlevitation furnace, two species of samples are heated with superimposed,the sample melted in first due to difference of electrical resistancesis adhered the one which is not melted yet, and then both of the samplesare levitated as a unit and are melted as a whole to fuse together. Onthe grounds of above, there is a problem that such fusion does notregard as a fusion in a state excluded from external interference (i.e.in a state avoided the use of a container), and there is also a furtherproblem that each of temperatures of two species of samples is notadjusted independently.

It comes near to stating the obvious that even if using anelectromagnetic levitation furnace, it is extremely difficult to makenonconductors fuse due to nonconductor is levitated only in beingmelted. This is a subject to solve these problems.

DISCLOSURE OF THE INVENTION

The present invention has been made in view of the problems in such aconventional art and an object of the invention is to provide aelectrostatic levitation furnace which, for example, when fusing twospecies of samples together, irrespective of whether or not the samplesare conductors, makes the samples melt while levitating themindividually and fuses the samples together while maintainingtemperatures of the samples respectively, and consequently actualize afusion in a state excluded external interference, and a method forfusing plural species of samples all together using the same.

The present invention is an electrostatic furnace which is provided witha vacuum chamber, main electrodes opposed each other within the vacuumchamber, an auxiliary electrode which displaces a sample levitated by aelectrostatic field generated between the main electrodes to apredetermined position, and a laser irradiator which irradiates a laserbeam on the sample displaced into the predetermined position to melt thesample, wherein a plurality of the main electrodes are arranged atproper intervals in a vertical direction to form electrostatic fieldgenerating interspaces between adjacent main electrodes respectively,the auxiliary electrodes are arranged to correspond to each of theelectrostatic field generating interspaces, the laser irradiators arearranged above the uppermost main electrode and under the lowest mainelectrode respectively so as to be opposed to each other coaxially, andthe main electrode positioned midway between the uppermost one and thelowest one has a through-hole on optical path of laser beam which asample can be passed through.

In preferred embodiment of the present invention, the electrostaticlevitation furnace includes a vacuum chamber, main electrodes opposed toeach other within the vacuum chamber, an auxiliary electrode whichdisplaces a sample levitated by a electrostatic field generated betweenthe main electrodes to the predetermined position, and a laserirradiator which irradiates a laser beam on the sample displaced intothe predetermined position to melt the sample, wherein a plurality ofpairs of main electrodes forming electrostatic field generatinginterspaces are stacked vertically, and also auxiliary electrodes arearranged to correspond to each of electrostatic field generatinginterspaces, the laser irradiators are arranged above the uppermost mainelectrode and under the lowest main electrode respectively so as to beopposed to each other coaxially, the main electrode positioned midwaybetween the uppermost one and the lowest one has a through-hole onoptical path of laser beam which a sample can be passed through. Formore preferred embodiment of the present invention, the electrostaticlevitation furnace is provided with an image pickup device so as toextend to adjacent electrostatic field generating interspaces, whichincludes a complementary metal oxide semiconductor (CMOS) camera or acharge coupled device (CCD) camera photographing a sample, a backgroundlight source irradiating a light on the sample, and a digital signalprocessor which executes image processing for edge enhancement in realtime and outputs a position of the center of gravity of the samplemaintained in a levitation state.

On the other hand, a method for fusing plural species of samples alltogether using the electrostatic levitation furnace of the presentinvention comprises, in fusing plural species of samples all togetherusing either one of the electrostatic levitation furnace mentionedabove, a step for levitating a first sample on the optical path of alaser beam in either one of electrostatic field generating interspacesand then irradiating a laser beam on the first sample from a laserirradiator of either side of main electrodes to melt the sample, a stepfor, while levitating the first sample which is kept in a melted stateto be irradiated a laser beam, levitating a second sample on the opticalpath of a laser beam in another one of the electrostatic filedgenerating interspaces and then irradiating a laser beam on the secondsample from a laser irradiator of the other side of main electrodes tomelt the second sample, a step for moving the sample from the upper oneof the electrostatic field generating interspaces levitating each of thefirst and the second sample in a melted state through a through-hole inmain electrode placed midway to an electrostatic field generatinginterspace placed lower and then fusing the melted samples together inkeeping a levitation state, a step for stopping both of the irradiationof laser beam from the upper and the lower laser irradiators to solidifyan fused body from the first and the second samples and then moving thefused body at a predetermined position within an electrostatic fieldgenerating interspace placed lower, and wherein plural species ofsamples are fused all together through the aforementioned steps.

The electrostatic levitation furnace of the invention has pluralelectrostatic field generating interspaces and auxiliary electrodescorresponded to each of the electrostatic field generating interspaces.This enables to levitate and move plural species of samples in each ofthe electrostatic field generating interspaces. To irradiate a laserbeam on each of the samples levitated in electrostatic field generatinginterspaces from each of laser irradiators at the side of mainelectrodes placed uppermost and lowest respectively enables to melt thesamples levitated individually and keep the temperature of the samples.In the above-mentioned situation, the sample positioned upper is moveddown, with controlling a temperature and a fall velocity of the sample,from the upper electrostatic field generating interspace through athrough-hole of the mid main electrode to the lower electrostatic fieldgenerating interspace, and then the samples in melted states are fusedtogether in holding levitated.

Since plural species of samples are levitated in each electrostaticfield generating interspace individually until being fused together, forexample, disposing an image pickup device so as to extend to twoadjacent electrostatic field generating interspaces due to obtain theposition information of a sample, one image pickup device can capture asample in one electrostatic field generating interspace and a sample inanother one individually and accordingly there is no need to dispose theimage pickup devices as many as electrostatic field generatinginterspaces. This enables to downsize the electrostatic levitationfurnace.

In more preferred embodiment of the present invention, an electrostaticlevitation furnace has the function of capturing plural species ofsamples individually using a CMOS camera or a CCD camera as a imagepickup device provided to extend to adjacent electrostatic fieldgenerating interspaces and sampling position information of the samplesat high velocities of about 1 kHz by executing image processing ofdigital signal processor.

A method for fusing samples together using the electrostatic levitationfurnace of the invention is adopted the above constitution, whichenables to melt plural species of samples while levitating themindividually and to fuse them all together while keeping the temperatureof each sample.

BRIEF DESCRIPTION OF THE INVENTION

FIG. 1 is an explanatory diagram of arrangement of main electrodes andauxiliary electrodes showing one embodiment of an electrostaticlevitation furnace of the present invention;

FIG. 2 is a cross-sectional explanatory diagram of the electrostaticlevitation furnace showing FIG. 1;

FIG. 3 is a schematic vertical sectional view of the electrostaticlevitation furnace showing FIG. 1;

FIGS. 4A to 4D are an process explanatory diagrams of steps for fusingtwo species of samples together using the electrostatic levitationfurnace showing FIG. 1; and

FIG. 5 is a schematic vertical sectional view of showing anotherembodiment of an electrostatic levitation furnace of the presentinvention.

BEST MODE FOR CARRYING OUT THE INVENTION

The present invention will be explained below with referring to theaccompanying drawings. It is to be understood that a detailedconstitution of an electrostatic levitation furnace of the invention isnot limited to the only following embodiments.

FIGS. 1 to 4 show one embodiment of an electrostatic levitation furnaceof the present invention. As shown FIGS. 1 to 3, the electrostaticlevitation furnace 1 is provided with a vacuum chamber 2 (shown in FIG.2 only), plural (three, in this embodiment) sheets of disc-form mainelectrodes 3 provided at intervals of 5 to 10 mm in a vertical directionwithin the vacuum camber 2, where an interspace between the adjacentmain electrodes 3 and 3 is defined as an electrostatic filed generatinginterspace A.

The electrostatic levitation furnace 1 is provided with an auxiliaryelectrode 4 displacing a levitated sample S to a predetermined position(on P axis passing through the centers of main electrode 3) byelectrostatic field generated in an electrostatic filed generatinginterspace A between main electrodes 3 and 3, and a laser irradiator 5irradiating a laser beam La on a sample S displaced the predeterminedposition to melt the sample.

The auxiliary electrodes 4 are arranged in pairs each of on Q axis andon R axis which cross each other at right angles on a plane orthogonalto the arranging direction of main electrodes 3, i.e. on a planeorthogonal to P axis. The laser irradiators 5 are arranged both of theupper side 3U of a uppermost main electrode (i.e. one main electrode)and the lower side 3L of a lowest main electrode (i.e. the other mainelectrode) so as to be opposite to each other on P axis.

In this case, the uppermost main electrode 3U and the lowest mainelectrode 3L are connected with high-speed and high-voltage amplifiers 6respectively, and the mid main electrode 3C between the uppermost oneand the lowest one has a through-hole 3 a which a sample S can be passedthrough at the center which P axis passes through, i.e. at the centerwhich corresponds to on an optical path of laser beam La.

The electrostatic levitation furnace 1 is provided with an image pickupdevice 10 disposed to extend to two electrostatic field generatinginterspaces A and A. The image pickup device 10 includes a CCD camera 11(or a CMOS camera) which photographs samples S and S levitatedindependently in electrostatic field generating interspaces A and A, ametal halide light source 12 which is placed on the opposite side of asample S from a CCD camera 11 and irradiates a light in a wavelength of400 to 450 nm on a sample S to act as a background light source, and adigital signal processor (not shown) which executes image processingenhancing the edge of an image captured by a CCD camera 11 in real timeand outputs a position of the center of gravity of a levitated sample S.Two sets of image pickup devices 10 are arranged to be orthogonal toeach other.

A reference number of 3 b in FIG. 1 and FIG. 3 denotes a sample placingspot.

Next, a procedure for fusing samples together using the electrostaticlevitation furnace 1 with above constitution will be illustrated.

In a first step shown FIG. 4A, after a first sample S1 (S) which isinputted into a electrostatic field generating interface A positioned atlower in two is charged, while a sample S1 is put a levitation state bya electrostatic field generated in a electrostatic field generatinginterspace A between main electrodes 3C and 3L, the sample S1 isdisplaced and maintained at a predetermined position P by controllingelectric potential of difference between main electrodes 3C and 3L andbetween auxiliary electrode 4 and 4, and then, in this state, the firstsample S1 is irradiated with a laser beam La from the lower laserirradiator 5 to melt the same.

In a second step shown FIG. 4B, while the first sample S1 which ismaintained in a melted state by irradiating a laser beam La on thesample is being levitated at the predetermined position P, a secondsample S2 (S) which is inputted into the upper electrostatic fieldgenerating interspace A is charged. Subsequently the second sample S2 isput in a levitation state by electrostatic field generated theelectrostatic field generating interspace A between main electrodes 3Cand 3U, the sample S2 is displaced and maintained at the predeterminedposition P by controlling electric potential of difference between mainelectrodes 3C and 3U and between auxiliary electrodes 4 and 4, and thesecond sample S2 is irradiated with a laser beam La from the upper laserirradiator 5 to be melted.

In a third step shown FIG. 4C, the second sample S2 is moved from theupper electrostatic field generating interspace A levitating the sampleS2 through the through-hole 3 a of the mid main electrode 3C to thelower electrostatic field generating interspace A while controlling thetemperature, position, and fall velocity of the sample S2, and thesamples S1 and S2 in melted states are fused together in retaining inlevitation states.

In a fourth step, stopping both irradiation of laser beam La from theupper and the lower laser irradiators 5 and 5, a fused body S′ from thefirst sample S1 and the second sample S2 is solidified and the sample S1is moved at a sample placing spot 3 b in the lower electrostatic fieldgenerating interspace A by controlling electric potential of differencebetween main electrodes 3C and 3L and between auxiliary electrodes 4 and4.

In the above mentioned steps, through capturing the samples S1 and S2individually by each of CCD cameras 11 on two sets of image pickupdevices 10 orthogonal to each other disposed to extended to twoelectrostatic field generating interspace A and A and sampling each ofposition information of the samples S1 and S2 at high velocities ofabout 1 kHz by executing image processing in digital signal processor,the position of the samples S1 and S2 are always recognized.

As mentioned above, the electrostatic levitation furnace 1 of theembodiment and the method for fusing samples together using the samehave the function of melting samples S1 and S2 kept levitatedindividually regardless of whether or not the samples S are conductorand fusing the samples S1 and S2 together while maintaining eachtemperature of the samples, and therefore achieve a fusion of thesamples S1 and S2 in a state avoided the use of a container.

In the electrostatic levitation furnace 1, since the samples S1 and S2are levitated in each electrostatic field generating interspace A and Aindividually, the first sample S1 and the second sample S2 can becaptured individually by two sets of image pickup devices 10 and 10disposed to extend to electrostatic field generating interspaces A and Aorthogonal to each other, the entire electrostatic levitation furnace isdownsized by reduction the number of the image pickup devices, and itbecomes possible that each of the position information of the samples S1and S2 levitated in two electrostatic field generating interspaces Arespectively is sampled at high velocities.

The above-mentioned embodiment shows the case that the first sample S1inputted into the lower electrostatic field generating interspace A oftwo is melted and subsequently the sample S2 inputted into the upperelectrostatic field generating interspace A is melted, however, it ispossible that a second sample S2 inputted into the upper electrostaticfield generating interspace A is melted first or both of samples S1 andS2 are melted simultaneously.

FIG. 5 shows another embodiment of an electrostatic levitation furnaceof the invention. An electrostatic levitation furnace 21 of thisembodiment is different from the electrostatic levitation furnace 1 ofthe preceding embodiment in that two pairs of main electrodes 23 and 23,each pair forms an electrostatic field generating interspace A, arelaminated with sandwiching insulating layer 27 in vertical direction, ahigh-speed and high-voltage amplifier 6 is connected to the mainelectrodes 23, and a through-hole 27 a of the approximately equal sizeof the through-hole 23 a provided in the mid main electrode 23 isprovided in an insulating layer 27. Other constitution of theelectrostatic levitation furnace of this embodiment is equal to thepreceding one.

The electrostatic levitation furnace 21 also has the function of,regardless of whether or not the samples S are conductors, melting thesamples S1 and S2 being levitated individually and fusing the samples S1and S2 together while maintaining the temperature of the samplesrespectively, and therefore it becomes possible to fuse the samples S1and S2 together in a state avoided the use of container. Since thehigh-speed and high-voltage amplifiers 6 are connected to the mainelectrodes 23 respectively, it is possible to generate an electrostaticfield with high voltage potential without using an amplifier with highpeak voltage (for example, an amplifier with a peak voltage of 20 kV),i.e. it is possible to generate an electrostatic field with high voltagepotential using an amplifier with low peak voltage (for example, amamplifier with a peak voltage of 10 kV) which allows simplification of asystem.

Both of the above-mentioned embodiments show the case that twoelectrostatic field generating interspaces A are formed and two samplesS1 and S2 are fused together, but the present invention is not limitedto such case. It is possible to form a large number of electrostaticfield generating interspaces A by arranging a large number of mainelectrodes 3 and 23 and to fuse sequentially many species of samples Scorresponding amounts of these electrostatic field generatinginterspaces A.

INDUSTRIAL APPLICABILITY

As explained above, according to the electrostatic levitation furnace ofthe present invention and the method for fusing plural species ofsamples all together using the same, for example, when two species ofsamples are fused together, regardless of whether or not the samples areconductors, it is possible to melt the samples being levitatedindividually and to fuse the samples together while maintaining eachtemperature of the samples, and a quite excellent advantage can beobtained that a fusion in a state excluded external interference, i.e.in a state avoided the use of a container is actualized.

For example, only by installing an image pickup device for obtainingposition information of a sample to extend to two adjacent electrostaticfield generating interspaces, a sample in one electrostatic fieldgenerating interspace and a sample in the other one can be capturedindividually, and therefore a quite excellent advantage is obtained thata downsizing of an electrostatic levitation furnace can be actualizedbecause it is unnecessary to install image pickup devices correspondingamounts of electrostatic field generating interspaces.

In more preferred embodiment of the invention, a quite excellentadvantage is obtained that a downsizing of an entire electrostaticlevitation furnace is actualized and in addition each of positioninformation of samples levitated in a plurality of electrostatic fieldgenerating interspaces respectively can be sampled at high velocities.

1. An electrostatic levitation furnace comprising a vacuum chamber, mainelectrodes opposed to each other within the vacuum chamber, auxiliaryelectrodes which move a sample levitated due to an electrostatic fieldgenerated between the main electrodes to a predetermined position, andlaser irradiators which irradiate a laser beam on the sample displacedto the predetermined position to melt the sample, wherein a plurality ofthe main electrodes are arranged at proper intervals in a verticaldirection to form electrostatic field generating interspaces between theadjacent main electrodes respectively, the auxiliary electrodes arearranged to correspond to each of the electrostatic field generatinginterspaces, the laser irradiators are arranged both above an uppermostone of said main electrodes and under a lowermost one of said mainelectrodes to be opposed to each other coaxially, and one of said mainelectrodes positioned midway between the uppermost one and the lowestone has a through-hole which is on an optical path of laser beam andthrough which a sample can be passed.
 2. An electrostatic levitationfurnace comprising a vacuum chamber, main electrodes opposed to eachother within the vacuum chamber, auxiliary electrodes which move asample levitated due to electrostatic field generated between the mainelectrodes to a predetermined position, and laser irradiators whichirradiate the sample displaced the predetermined position to melt thesample, wherein plural pairs of the main electrodes formingelectrostatic field generating interspaces are arranged stacked in avertical direction, the auxiliary electrodes are arranged to correspondto each of the electrostatic field generating interspaces, the laserirradiators are arranged both above an uppermost one of said mainelectrodes under a lowermost one of said electrodes, and one of saidmain electrode positioned midway between the uppermost lowest one has athrough-hole on an optical path of laser beam which a sample can bepassed through.
 3. An electrostatic levitation furnace according toclaim 1 wherein an image pickup device comprising a CMOS camera or a CCDcamera photographing a sample, a background light source irradiating alight on a sample, and a digital signal processor executing imageprocessing which enhances the edge of an image in real time andoutputting a position of the center of gravity of a sample put in alevitation state is provided so as to extend to adjacent electrostaticfield generating interspaces.
 4. A method for fusing samples togetherusing an electrostatic levitation furnace, comprising, in fusing aplurality of species of samples all together using an electrostaticlevitation furnace according to claim 1; a step for levitating a firstsample on an optical path of a laser beam in either of pluralelectrostatic field generating interspaces and subsequently irradiatingthe laser beam on the first sample from a laser irradiator at the sideof one main electrode to melt the sample; a step for, while levitating afirst sample maintained in a melted state by irradiating a laser beam onthe first sample, levitating a second sample on an optical path of alaser beam in another of said electrostatic field generating interspacesand subsequently irradiating a laser beam on the second sample fromanother laser irradiator at the side of the other main electrode to meltthe sample; a step for moving the sample positioned in an upper one ofthe electrostatic field generating interspaces which levitate the firstand the second samples in melted states respectively from said upper oneelectrostatic field generating interspace through a through-hole of amain electrode positioned midway to said lower one electrostatic fieldgenerating interspace while controlling the temperature, position, andfall velocity of the sample, and subsequently fusing the samples inmelted states together while levitating them; a step for stoppingirradiation of laser beams from both the upper and the lower laserirradiators to solidify a fused body from the first and the secondsamples, and subsequently moving the fused body at a predeterminedposition in the lower electrostatic field generating interspace, whereina plurality of species of samples are fused all together through theabove-mentioned steps.